I’ve been trying to track this issue for quite a bit of time. What seems to be a problem is stock EFHK content.

You may try to move the files away (make a backup!).

X:\Prepar3D\Scenery\0601\scenery

APX54100.bgl
OBX54100.bgl
cvx5410.bgl (if using Orbx Vector)

The alternative is to download our modified file – cvx5410.bgl and replace it.

Look at the OBX54100 which has a lot of stock scenery objects placed all around. Each of them takes a draw call or more.